Manufacture of tubes



C. A. ORR ETAL MANUFACTURE OF TUBES March 10, 1942.

a Sheets-Sheet 1 Filed Nov. 21, 1958 I. Qwum/bm [dim/1d March 10, 1942. c, A ORR ETA'L' 2,275,801

' MANUFACTURE OF TUBES 3 Sheets-Sheet 2 Filed Nov 21, 1938 March 10, 1942.- c. A. ORR arm.

MANUFACTURE OF TUBES- 7 Filed Nov. 21, 1938 3 Sheets-Sheet 3 awe/whom Patented Mar. 10, 1942 UNITED STATES PATENT OFFICE MANUFACTURE OF TUBES poration of Ohio Application November 21, 1938 Serial No. 241,580

3 Claims.

The invention relates to tubes, pipes, poles,

shafts and the like; and particularly to seamless steel tubes and to a method of cold rolling the same. However, the method and product improvements hereinafter described are equally applicable' to the manufacture of welded tubes,

pipes, poles, shafts and the like made from metal sheets, strips, stripsheets and the like.

The use of steel pipes or tubes having relatively large diameters and relatively thin walls for many purposes,'such as for water pipes and for oil well casings, is largely determined by the physical properties of the steel. These-physical properties may be changed for any given pipe size and wall thickness to increase the strength thereof by changing the analysis of the steel. However, a change in the steel analysis is sometimes undesirable, because of the prohibitive'cost of using expensive alloying elements; and because of the diminished weldability of the special analysis steel selected, as welding is frequently required in connection with the installation of such tubes. u

The strength of a steel. tube of any given analysis and diameter may be increased by increasing the wall thickness thereof; but such a change is objectionable due to the cost or weight 7 of the increased amount of metal present therein.

In numerous instances it has been proposed to change the physical properties of a tube by squeezing or pressing a tube while cold between two semi-cylindrical dies to slightly decrease the diameter of the tube. Such a cold pressing operation may increase the yield point of the tube wall in compression in a circumferential direction to a considerable extent but it only slightly increases the yield point of the metal in tension in a longitudinal direction; and in any event the resulting yield point in tension in a longitudinal direction is less than the resulting yield point in compression in the circumferential direction.

Moreover, such a cold pressing operation .may increase variations in wall thickness, may increase out-of-round imperfections, and, due to the very nature of such a pressing operation in acting radially at some places and tangentially at other places upon a tube wall, does not uniformly alter the physical properties.

Over eighty years ago it was proposed to hot roll seamless tubes by pointing a tube blank and passing the same on a mandrel through a series thickness of the tube blank. In'such process the reasons if used as a cold rolling process.

mandrel engages the pointed end of the tube blank to pull thesame through the rolls. The seamless tube so treated is finally drawn through a suitable die to size thesame and provide a. smooth finish.

Such a process is primarily a hot rolling process; and would be impractical for a number of ltially, a pointing of the tube blank is required, which not only increases expense, but decreases yield. Moreover, the mandrel, in engaging the pointed tube end, places the tube walls under longitudinal tension as the rolls are working the tube wall metal against the mandrel, so that grain distortion may result.

Moreover, while the yield point in tension in a longitudinal direction may be increased somewhat by such a cold working operation, no appreciable change will occur in the yield point in compression in a circumferential direction. Finally, it is practically impossible to uniformly load a plurality of mechanically adjusted radially seamless tubes for reducing'the diameter and thickness of the tube walls by passing the same through a series of upper and lower, concaved,. half-round, driven rolls. However, it is substantially impossible to drive such rolls and'load them uniformly; and by their very nature concaved rolls exert unequal pressures upon the tube walls, so that the resulting product is not evenly and uniformly worked and the wall thickness'and uniformity thereof cannot be accurately controlled.

Such an operation may increase the yield point in tension in a longitudinal direction to some extent, but it has little or no effect upon the yield point in compression in a circumferential direction. In such an operation, the tube wall is not under longitudinal tension or compression ,throughout its length while being worked, al-

though a small zone of the same may be under longitudinal tensionwhile being worked radially due to the action of the driven rolls in advancing the material therethrough.

The prior Riemenschneider Patent No. 1,984,-

For these and other reasons, whenever the wall thicknesses or diameters of seamless tubes have been increased or decreased to any appreciable extent, the same has usually been accomplished by a hot working operation; and substantially all cold working operations on seamless or electric welded pipes or tubes have been merely for the purpose of shaping, sizing or straightening the tubes. Such cold working operations, as previously pointed out, may raise the yield point in tension in a longitudinal direction, but do not appreciably affect the yield point in compression in a circumferential direction.

In' the piror art cold pressing operation referred to, while the yield point in compression in a circumferential direction is raised, the resulting yield point in tension in a longitudinal direction is less than the yield point in compression in a circumferential direction.

Finally, except when using the method shown in the Riemenschneider Patent No. 1,984,083, and possibly when using acold drawing operation, the prior art methods of cold working a pipe or tube do not uniformly work the materialdue to the impossibility of uniformly loading driven rolls, or of uniformly loading a plurality of mechanically controlled radially acting rolls, or of uniformly loading dies which act radially at some places and tangentially at other places on e metal being worked; and in the excepted instances, the metal being worked is maintained under longitudinal tension.

Accordingly, it is an object of the present inventionto provide a method of cold working tubes, particularly seamless tubes, to provide a strong thin walled steel tube of relatively large diameter that has good welding cliaracteristics..

Moreover, it is an object of the present invention to provide a method of cold working tubes, particularly seamless tubes, by performing a cold working operation while the tube walls being.

worked are maintained under longitudinal compression.

Likewise, it is an object of the present invention to provide a method of cold working tubes, particularly seamless tubes, by using radially acting rolls which may be uniformly loaded to pro-- vide a balanced working pressure against a mandrel, so that the thickness, and the uniformity of thickness, of the tube walls being worked may be controlled or improved; and so that the strength the yield point in compression in a circumferential direction is substantially increased, by which the yield point in tension in a longitudinal direction is also substantially increased, and by which the yield point in tension in a longitudinal direction is increased to a point substantially greater than the yield point in compression in a circumferential direction.

Moreover, it is an object of the present invention to provide for the manufacture of a steel tube, particularly a seamless tube, which is cold worked, to materially increase the yield point in tension in a longitudinal direction and the yield point in compression in a circumferential direction; to decrease extreme variations in wall thickness; and to decrease the cost of making strong, large diameter tubes without loss of yield; whereby such tubes may be made available for use in places and for purposes from which they have heretofore been excluded.

And finally, it is an object of the present invention to overcome the diificulties encountered in the prior art of cold working pipes or tubes; to simplify the manufacture of the same; to provide an improved cold rolled tube product; and generally to obtain the desiderata referred to hereinabove.

The foregoingand other objects may be obtained by the tube products, constructions, parts, arrangements, improvements, methods, processes and operations which comprise the present invention, the nature of which is set forth below in general statements.

Some of the features and operations of the improved method are illustrated in the accompanying drawings, showing more or less conventionally or diagrammatically, details of apparatus by which they may be performed; and the invention is particularly and distinctly pointed out and set forth in the appended claims forming part hereof.

The nature of the method improvements of the present invention may be described in general terms as including in the manufacture of cold worked steel tubes, the steps of cold rolling the tube on a mandrel, uniformly loading the rolls so that balanced working pressures are exerted by the rolls during the cold rolling operation, and during each pass maintaining the unworked portion of the tube walls and especially the portion being worked under longitudinal compression while the cold rolling operation is being performed; whereby the tube will be materially elongated and reduced in diameter.

The nature of the improved tube products of the present invention may be described in general terms as including a steel tube, the metal of which has been cold worked, to raise its yield point in compression in a circumferential direction 40 per cent or more, to raise its yield point in tension in a longitudinal direction 30 per cent or more, and to have a substantially greater yield point in tension in a longitudinal direction than the yield point in compression in the circumferential direction.

In the drawings, a Figure 1 is a side view of a seamless tube prior to being cold worked by the improved method;

Fig. 2 is a similar view of a seamless tube after being cold worked by the improved method;

Fig. 3 is a similar view of an electric welded tube prior to being cold worked by the improved method;

Fig. 4 is a similar view of the tube shown in Fig. 4 after being cold worked by the improved method;

14 because the mandrel Figs. 5, 6, 7 and 8 are enlarged sections taken respectively on the lines -5, 6-6, 'I.-1 and 8-8, Figs. 1, 2, 3 and 4;

Fig. 9 is a diagrammatic cross section of the cold rolling apparatus;

Fig. 10 is a diagrammatic longitudinal section of the apparatus shown in Fig. 9; and

Fig. 11 is a diagrammatic view of a modified form of mandrel.

Similar numerals refer to similar parts throughout the several figures of the drawings.

A seamless cylindrical steel tube is indicated at in Figs. 1 and 5 and the same may be a almost any diamusual seamless tube product of eter say beyond- 3 inches in outside diameter and having almost any desired wall thickness ranging from approximately 1% inches to of an inch or even more.

The tube II may be placed on the cylindrical mandrel .I2 of a machine generally of the type shown in the Frahm Patent No. 1,605,828, or the Riemenschneider Patent No. 1,984,083, for being cold worked thereon, the'mandrel being somewhatsmaller in diameter than the tube. Sucha-machine must, however, have certain modifications in order to accomplish the objects and carry out the method to the present invention.

The mandrel I2 must be provided with a collar produce the product ofv I3 or other enlarged means against whichan end of the tube I I may be abutted as at I I. With this arrangement, as the mandrel is moved in the direction of the arrow of 10, the cold roller swaging dies I5, roll, swage and cold work the tube against themandrel l2 to elongate the tube and decrease its diameter.

While the radial working of the tube metal by the rolls I5 is being performed, the tube wall is maintained under longitudinal compression between the bite of the rolls I5 and the shoulder shoulder I4 is engaged against the left hand ,end of the tube II for pushing the tube through the rolls.

The tube I I may be pushed through the rolls I5 any number of times or passes, say from 1 to 10 or more passes, but preferably 2 or 3 passes, depending upon the reduction in diameter to be accomplished by the cold rolling operation and the amount it may be desired to change the thickness of the tube wall.

Due to the fact that the radially acting rolls I5 are each hydraulically controlled by a fiuid cylinder, all of which roll cylinders are connected with a suitable single source of fluid pressure such as water, oil, compressed air or the like, the rolls I 5 are all uniformly loaded and exert a uniform or balanced working pressure during the cold working operation so that the cold working of the the rolls out.

metal of the tube wall between I5 and mandrel I2 is uniform through- As a result, any thickening or thinning of the ube wall is uniformly accomplished and if the tube wall of the initial tube I I has the usual variations in thickness present in seamless tubes, the range of the extreme'variations is materially diminished by the uniform cold working of .the metal while the metal is under longitudinal compression between the bite of the rolls I5 and the pushing or advancing shoulder I 4.

As previously stated, this cold working of the metal in the tube wall 'elongates the tube II to a considerable extent, such as is indicated by the finished cold rolled tube I6 shown in Figs. 2 and 6; and while the first pass of the-tube through the rolls I5 may thicken the tube wall somewhat due to the decrease in diameter thereof, subsequent passes cause further elongation of and thinning of the tube wall. Thus, the wall of the cold rolled tube [6 may be thicker or thinner' than that of the initial tube I I, as desired.

In Figs. 3 and 7, a welded tube made of sheet ,metal is shown at II a, which may be treated in a manner similar to the treatment of the seamless tube II to produce a cold rolled welded tube product I6a illustrated in Figs. 4 and 8.

In Fig. 10, the mandrel is shown as only being capable of moving in one direction for performing a. cold rolling operation; but the mandrel construction may be modified, as shown in Fig. 11, to include a stop or abutment shoulder 23 having a stripper stop or abutment ring 24 whereby the cold rolled tube may be stripped from the mandrel. A plug 25 is also provided at the other end of the mandrel having an abutment shoulder. 26 whereby the mandrel may be moved back and forth through rolls I5 to perform a cold rolling operation in each direction of movement. Obviously, the stops 24 and 26 must be located further apart than the resultant length of the finished tube I 6.

Examples of products made by, treating them in accordance with the improved method are as follows Example 1 square inch, and an average yield point in compression in a circumferential direction of 51,360

pounds per square inch, with an average elongation in 2 inches of approximately 30 per cent, were cold rolled in accordance with the improved method from,2 to 10 passes on a 10%;" diameter mandrel.

The resulting cold rolled tubes had an average resulting outside diameter of 11.433 inches, an

actual average gauge of .426 inch, an average I tensile strength of 94,520 pounds per square inch, an average yield point in tension in a longitudinal direction of 83,040 pounds per square inch, and an average yield point in compression in a circumferential direction of. 76,780 pounds per square inch, with an average elongation in 2 inches of about 25 per cent.

Thus, the longitudinal tensile yieldpoint was increased :approximately 33 per cent, while the transverse compressive yield point was increased about 49 per cent with .the resulting longitudinal tensile yield point considerably above the resulting transverse compressive yield point; and

- the ultimate tensile strength was raised nearly-7 per cent. a

Ductility and resistance to impact were somewhat reduced, as would be expected, while the residual stress as measured by a split ring test, was improved by being diminished; and extreme variations ingauge were likewise improvedby being diminished about 50 per cent. In this Example 1 the average reduction in diameter was about 3.97%.

(actual measured average gauge.

Example. 2

gauge-.320 inch), having an average yield point in tension in a longitudinal direction of 63,190 pounds per square inch, and an average yield point in compression in a circumferential direction of 55,680 pounds per square inch, with an average elongation in 2 inches of approximately 32/2%, were cold rolled in accordance with the improved method some 9 passes on a diameter mandrel.-

The resulting cold rolled tubes had an average resulting outside diameter of 11.193 inches, an actual average gauge of .340 inches, an average tensile strength of 100,680. pounds per square inch, an average yield point in tension in a longitudinal direction of 91,650, and an average yield point in compression in a circumferential direction of 83,300 pounds per square inch, with an average elongation in 2 inches of about 25%.

Thus, the longitudinal tensile yield point was increased about 45%, while the transverse compressive yield point was increased about 51% with the resulting longitudinal tensile yield point considerably above the resulting transverse compressive yield point, and the ultimate tensile strength was raised about 11%. Ductility and resistance to impact were somewhat reduced, as would be expected, while the residual stress as measured by a split ring test, was improved by being diminished slightly; and the extreme variations in gauge were likewise improved by being diminished about 50%. In this Example 2, the average reduction in diameter was about 5.23%. In both Examples Land 2, the tubes were elongated from 4 to 8 inches in a 40 foot length.

Example 3 Electric welded pipes having an analysis of 0.05 carbon, 0.31 manganese, 0.014 phosphorus and 0.031 sulphur, having a minimum tensile strength of about 45,000 pounds per square inch, having a nominal outside diameter of 11 inches, having a nominal gauge of .134 inch, and having an average yield point in tension in a longitudinal direction of approximately 32,000 pounds per square inch and a yield point in compression of approximately 32,000 pounds per square inch, were cold rolled in accordance with the improved method from 6 to 10 passes on a 101% diameter mandrel.

The resulting coldrolled tubes had an average resulting outside diameter of 10.765 inches, an actual average gauge of .135 inch, an average tensile strength of 55,000 pounds per square inch. an average yield point in tension in a longitudinal direction of 52,880 pounds per square inch,

and an average yield point in compression in a circumferential direction of about 50,000 pounds per square inch, with an average elongation in 2 inches of approximately 28%.

- Thus, the tensile yield point was increased approximately 65%, while the transverse compressive yield point was increased about 56% with the resulting longitudinal tensile yield point above the resulting transverse compressive yield point; and the ultimate strength was raised about 22%. Accordingly, by using the improved method of cold rolling metal tubes, particularly seamless tubes, a strong thin walled steel tube of relatively large diameter having good welding characteristics may be made; a tube having a uniform strength in a longitudinal direction and also a uniform strength in a transverse direction may be made; the thickness of the tube wall, and the uniformity of the thickness thereof, may be controlled or improved; the yield point in tension in a longitudinal direction may be substantially increased, and the yield point in compression in a circumferential direction may also be substantiallyincreased; and the manufacture of such tubes and the product thereof may be generally improved.

Moreover, the amount that the longitudinal tensile yield point is raised may be controlled by the amount of cold rolling performed; and the amount that the transverse compressive yield point is raised may be controlled by the amount that the diameter of the tube is reduced.

Having'now described the features of the invention, the operation and use of the preferred method, the characteristics of the improved product obtained, and the advantages and results occurring in the use of the method and in the product; the new and useful parts, elements. combinations, constructions, methods and steps and the reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.

We claim:

1. The method of cold working metal tubes including the steps of placingv a tube on a smaller diameter mandrel, radially working the tube wall metal under pressure between the mandrel and rolls by passing the tube and mandrel between radially acting rolls, maintaining balanced working pressures on the tube wall metal during working by uniformly loading the rolls, and maintaining that portion of the tube wall being worked under longitudinal compression while radially working the same under balanced working pressures.

2. The method of cold working metal tubes including the steps of radially working the metal wall of a tube by passing the tube between radially acting rolls, maintaining balanced working pressures onthe tube wall metal during working by uniformly loading the rolls, and maintaining that portion of the tube wall metal being worked under longitudinal compression while radially working the same under balanced working pressures.

3. The method of cold working metal tubes including the steps of radially working the metal wall of a tube by passing the tube a plurality of times back and forth between radially acting rolls, maintaining balanced working pressures on the tube wall metal during working by uniformly loading the rolls, and during each pass maintaining that portion of the tube wall being worked under longitudinal compression while radially working the same under balanced working pressures.

CHESTER A. ORR. EDMUND W. RIEMENSCHNEIDER. 

